1. Field of the Invention
The present invention relates to a lead frame and a method of manufacturing the same, and a semiconductor device and a method of manufacturing the same.
2. Description of the Related Art
There has recently been a demand for reductions in size and thickness of a semiconductor device mounted on a board. In order to meet such a demand, various semiconductor devices of a so-called QFN (Quad Flat Non-lead) type have conventionally been proposed which are formed by using a lead frame, sealing a semiconductor element mounted on a mounting surface of the lead frame with a sealing resin, and exposing a part of leads on a rear surface side.
As QFN is becoming common, power supply ICs and analog ICs as general-purpose packages have been mounted in many electronic apparatuses. In addition, there has recently been an increasing demand for QFN packages to have a larger number of pins, and thus packages of 100- to 200-pin types to be used for advanced power supplies, microcomputers, and basebands for communication and radio has been developed.
However, the package of a QFN having a conventional ordinary structure becomes larger as the number of terminals increases, making it difficult to ensure mounting reliability. The larger size of the package lengthens distance between internal terminals and a semiconductor chip, and therefore increases an amount of usage of bonding wires made of gold, so that the manufacturing cost of the package rises. In addition, an increase in length of the bonding wires may cause a problem at a time of package assembly.
In order to deal with these disadvantages, a package referred to as a DR-QFN (Dual Row QFN) having external terminals arranged in two rows as a technology for realizing a QFN having a larger number of pins has been developed (see for example JP-3732987, JP-2001-189402-A, and JP-2006-19767-A). Such a DR-QFN is provided with half-etched lead portions for supporting inside terminals. The DR-QFN however has the number of lead portions larger due to an increase in the number of pins, the lead portions inevitably being required be designed to have a small width. The small width may make the strength of the half-etched lead portions insufficient, possibly deforming the lead portions to cause displacement of external terminals. The yield of the lead frame may be consequently decreased.